Magnetic combinatorial libraries have been fabricated to investigate complex magnetic thin-film systems and to provide test systems to develop on-wafer metrologies. The use of combinatorial materials techniques is a new and powerful method to develop and investigate magnetic thin-film systems which require ternary or quaternary alloys. Libraries were fabricated by co-depositing NiO.8 FeO.2, Co, and Tb in a system designed to provide compositional gradients across the wafer. The initial libraries consist of 20x20 sites, each marked with an identification number. The composition varies across the wafer with compositions of TbO.60 (NiFe) 0.10Co).30, Tb0.22(NiFe)0.22Co0.56, Tb0.10(NiFe)0.65Co0.25 at the Tb, Co, NiFe rich corners respectively. The purpose of this particular library was to investigate optimal magnetostrictive thin films which have large magnetostriction yet relatively small saturation fields and to look for compositions that have large magneto-optical effects.